Signal generating apparatus

ABSTRACT

A missile fuze arrangement in which a change in capacitive coupling between two mutually insulated conductive areas on the missile skin, arising from contact of one of those areas with a target body, results in a change in alternating current flow through that coupling from a generator to a load, the change in current flow providing an output signal to detonate the warhead of the missile.

United States Patent Davies et al.

v June 13, 1972 SIGNAL GENERATING APPARATUS Inventors: Robin John Davies, Lenham, near Maidstone; William Kenneth Capewell, Maidstone, both of England Assignee: Elliott Brothers (London) Limited, London, England Filed: March 11, 1970 Appl. No.1 18,518

US. Cl. 102/702 R Int. Cl ..F 42b 5/08 Field of Search ..3 1 7/146; 340/258 C; l02/70.2

[ 56] References Cited UNITED STATES PATENTS 2,782,308 2/ 1957 Rug ..340/258 C 3,382,408 5/1968 Atkins ..3 17/146 Primary Examiner-Samuel Feinberg Att0mey-Kirschstein, Kirschstein, Ottinger & Frank [57] ABSTRACT A missile fuze arrangement in which a change in capacitive coupling between two mutually insulated conductive areas on the missile skin, arising from contact of one of those areas with a target body, results in a change in alternating current flow through that coupling from a generator to a load, the change in current flow providing an output signal to detonate the warhead of the missile.

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whim 025 Poe/v t/omv a we: zumvr K211106774 Caren F44 EZLLL, flue 4 This invention relates to apparatus for generating a signal, particularly though not exclusively with a system for use in a projectile or missile (hereinafter called a missile) in which a detonation of an explosive charge carried by the missile occurs as a result of contact between the missile and an object, e.g., a target.

According to the invention apparatus for generating a signal upon contact or loss of contact between a body whose selfcapacitance is in excess of a certain value and either one of two electrically conductive, electrically isolated relatively fixed parts, comprises an alternating current source connected between the said two parts through a load; and means for detecting the change in load current which occurs as a result of change in capacitance at said contact or loss of contact.

According to another aspect of the invention a missile has a skin which comprises two electrically conductive, electrically isolated, relatively fixed parts, an alternating current source connected between the said two parts through a load, and means for detecting the change in load current which occurs as a result of change in capacitance at contact between either one of said parts and a body whose self-capacitance is in excess of a certain value.

The voltage developed across the load may be applied to a summing amplifier which also receives a voltage signal derived from the source and phase related with the voltage applied, by the source, between the said two parts so that, until contact or loss of contact occurs between either of those parts and the said body, the output signal from the summing amplifier is substantially at null. This may, conveniently, be achieved by a voltage phase controller connected between the source and the summing amplifier and operable in response to a feedback signal from the amplifier output to produce a voltage signal whose phase relationship to the voltage applied to the amplifier from the load is such that, until contact or loss of contact occurs between a said part and the said body, the output signal from the amplifier is at null.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which:

FIG. 1 shows schematically a plan view of a part of the surface of a missile;

FIG. 2 shows schematically a sectional view of the part shown in FIG. 1, and

FIGS. 3. to 7 show diagrammatically five different missile fusing systems in accordance with the invention.

Referring first to FIGS. 1 and 2, the missile surface has two electrically conductive, electrically isolated relatively fixed parts 1 and 2. Conveniently, the part 1 is in the form of a small disc of metal which is let into an aperture in the other, the main body part 2 of the skin and supported with respectto the main body portion by an annulus 3 of dielectric material.

Located within the missile, there is circuitry 4 which as shown in FIG. 3 comprises an alternating current generator 5 connected in series with a load resistor 6 between the two parts 1 and 2. As shown schematically, in FIG. 3, the mutual capacitance 7 between the electrically isolated skin parts 1 and 2 appears acrossthe series-connected generator 5 and load resistor 6. The self-capacitance 8 of the disc 1 and the self-capacitance 9 of the main body part 2 of the missile skin may be represented as shown.

In a typical case the capacitance 7 would be of the order 5pF, capacitance 8 would equal 5pF also and capacitance 9 would be of the order 50pF. If the generator 5 develops 100 volts r.m.s. at a frequency of say 500 kilol-Iertz and the resistor 6 has a value 2 K ohms, then an alternating voltage of 10 volts would be developed across the resistor 6. If the missile comes into contact with a body, the target, the self-capacitance of which, represented in FIG. 3 by the capacitor 10, is of the order of hundreds of picofarads then the alternating voltage across the resistor 6 changes by nearly 5 percent, i.e., by 0.5

volts. This change in voltage across the load resistor 6 is detected by a suitable detector/amplifier 11 and the output of this detector/amplifier 11 IS emp oyed in triggering an explosive charge (not shown) carried by the missile.

If the missile is very large, so that the self-capacitance 8 of the disc 1 is vary small compared with the capacitance 9 of the main body part 2 of the missile, the arrangement shown in FIG. 4 may be preferred. In this arrangement the voltage developed across the load resistor 6 is effectively cancelled out in a summing amplifier 12 by an anti-phase signal from the generator 5. The use of this cancellation system also avoids problems arising from microphony in the generator 5 or amplifier 12. v

To simplify the problem of setting up a balance, a control loop may be employed as shown in FIG. 5. This control loop automatically detects any out of balance at the detector/amplifier 11 and controls the magnitude and phase of the balancing signal to ensure cancellation. The time constants of the control loop may be chosen such that they rapid change of signal that occurs at contact between a part 1 or 2 and a target passes through the receiver without substantial attenuation.

In the arrangements shown in FIGS. 3 to 5 there is a standing alternating current through the resistor 6, and as shown for example in FIG. 6 this current may be neutralized, or balanced, by employing an antiphase output from the generator 6 to supply alternating current through a capacitor 13. Complete neutralization is achieved when the value of the capacitor 13 equals the value of the capacitance 7 in parallel with the series combination of capacitances 8 and 9.

The circuit shown in FIG. 6 may be modified as shown in FIG. 7 to given a differential output on lines 14 and I5.

Whilst the invention has been described with reference to a missile and, more particularly, with the detection of contact between the missile and a target, other applications for the invention are contemplated. In particular, the invention can be utilized in detecting loss of contact between a body and either of two electrically conductive, electrically isolated, relatively fixed parts.

We claim:

1. Missile fuze apparatus for generating a'signal upon contact between a target body having a self-capacitance above a certain value and either one of two electrically conductive, mutually electrically insulated areas on the skin of the missile, comprising an alternating current source, a load, means connecting said source and said load in series between said two areas on the skin of the missile, and means to provide a warhead detonating signal in response to a change in load current occurring as a result of a change of capacitance between said two areas upon contact with the target body.

2. Missile fuze apparatus in accordance with claim 1 wherein said means to provide a detonating signal comprises a summing amplifier, means to apply the alternating voltage developed across the load to one input of said amplifier and means to apply to another input of said amplifier an alternating voltage from said source of phase and magnitude such as to balance out said load voltage in said summing amplifier.

3. Missile fuze apparatus in accordance with claim 2 wherein said means to apply a voltage to another input of said amplifier comprises phase control means connected between the source and said other input, said phase control means being responsive to an output from said amplifier to apply to said amplifier a signal whose phase relationship to the load voltage is such that until contact occurs between one of said areas and said target body the output signal from the amplifier is at a null.

4. Missile fuze apparatus in accordance with claim 1 comprising capacitive means to apply an alternating current from the source to the load in antiphase to the current flow to the load by way of said capacitance between the two areas of the skin of the missile, whereby in the absence of contact between one of said areas and a target body the overall load current is arranged to be substantially zero. 

1. Missile fuze apparatus for generating a signal upon contact between a target body having a self-capacitance above a certain value and either one of two electrically conductive, mutually electrically insulated areas on the skin of the missile, comprising an alternating current source, a load, means connecting said source and said load in series between said two areas on the skin of the missile, and means to provide a warhead detonating signal in response to a change in load current occurring as a result of a change of capacitance between said two areas upon contact with the target body.
 2. Missile fuze apparatus in accordance with claim 1 wherein said means to provide a detonating signal comprises a summing amplifier, means to apply the alternating voltage developed across the load to one input of said amplifier and means to apply to another input of said amplifier an alternating voltage from said source of phase and magnitude such as to balance out said load voltage in said summing amplifier.
 3. Missile fuze apparatus in accordance with claim 2 wherein said means to apply a voltage to another input of said amplifier comprises phase control means connected between the source and said other input, said phase control means being responsive to an output from said amplifier to apply to said amplifier a signal whose phase relationship to the load voltage is such that until contact occurs between one of said areas and said target body the output signal from the amplifier is at a null.
 4. Missile fuze apparatus in accordance with claim 1 comprising capacitive means to apply an alternating current from the source to the load in antiphase to the current flow to the load by way of said capacitance between the two areas of the skin of the missile, whereby in the absence of contact between one of said areas and a target body the overall load current is arranged to be substantially zero. 